It is not about being a gangster or being affiliated, it is the art in which you do something. An aggresive, robust way of being or doing something which is more often than not successful.
A: Van Persie's goal against Charlton was sick!
B: Van Persie is totally gangster.
A: I ride Mack hubs laced to Archetypes.
B: That's totally gangster.
A: Turkish Lira gained two points on Forex.
B: That's totally gangster.
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